Blackmagic RAW – Dynamic Range on the URSA Mini Pro 4.6 Tested

When Blackmagic RAW (BRAW) was announced a while ago, I was curious to get my hands on a BMD URSA Mini Pro and test it’s dynamic range with this new codec. The combination of having the full flexibility of 12bit RAW and smaller file sizes at the same time is a real innovation of BMD. How does it fare on the UMP 4.6?

A while ago BMD was so kind to send us the URSA Mini Pro 4.6 but unfortunately, we were all out traveling yet there was time to install the new firmware 6.0 and test the dynamic range at ISO 800 and 3200 using our test setup described here.

One note upfront: I was very surprised to see the playback performance of BRAW in DaVinci Resolve Studio 15.2. I am using an I7-4720HQ Laptop with 16GB RAM and a GTX980M graphics card, and 4.6k ProRes XQ resulted in ~7 frames / second playback (fps), 4.6k RAW DNG (lossless) resulted in ~11 fps, whereas BRAW had smooth 24 fps playback in a UHD timeline! Hence, not only smaller filesizes with BRAW but also vastly improved playback – a real winner combination.

4.6k ProRes XQ ISO 800 dynamic range results

As a baseline, we started first with our standardized testing procedure analyzing the 4.6k ProRes XQ dynamic range. Here, at ISO 800 the UMP 4.6 does not disappoint and comes in with a strong 12.5 stops of dynamic range at a signal to noise ratio of 2 according to our IMATEST analysis (13.6 stops at a signal to noise ratio of 1). I also tested ISO 400, which yielded slightly lower results. This is the best result in our recent 2018 testing, coming in half a stop higher than the Sony FS7. However, quite far from the 15 stops that Blackmagic Design claim. Anyways, we are going to test BRAW subsequently, so let’s see. The noise floor looks very clean, looks like some internal noise reduction is going on here.

Fig.1: Step chart waveform plot of the UMP 4.6k ProRes XQ at ISO 800: a little more than 12 stops can be discerned above the noise floor (code values scaled to 8bit).

4.6k BRAW dynamic range results

Now, there is a little issue with BRAW and our standardized testing workflow, as we usually try to avoid any 3rd party software when extracting keyframes for our IMATEST analysis (other than FFmpeg) to avoid any kind of manipulation/influence of this software to the image. With BRAW this philosophy doesn’t work, as we have to use DaVinci Resolve to develop the files – the latest version 15.2 Studio in our case.

ISO 800 BRAW constant bitrate 3:1 4.6k scaled to UHD

Now, using ISO 800 yielded again the best results, with the dynamic range coming in at an even stronger 12.6 stops at a signal to noise ratio of 2 (13.7 stops for SNR = 1). However, this slight difference to ProRes might be also a result of scaling the 4.6k BRAW file to UHD (3840×2160) – as there is no 4.6k timeline preset in DaVinci Resolve (for exporting keyframes to IMATEST).

NOTE: DaVinci Resolve offers a “highlight recovery” option for BRAW, which can reconstruct the RGB channels even if one channel is already clipped. Together with the noise reduction features, you can heavily post-process the BRAW files – I just tried around a little bit and was able to reach around 13 stops for SNR = 2 (14 stops for SNR = 1). However we don’t count this result as our intention is to test the untouched files straight off the camera – this is not a post-processing contest, it is about a standardized result using a standardized workflow for all the cameras we test.

ISO 3200 BRAW constant bitrate 3:1 4.6k scaled to UHD

For ISO 3200 we counted 11.7 stops for an SNR = 2 (12.9 stops for SNR = 1), again without post-processing. Playing around with the highlight recovery option and noise reduction, I was able to get around 12 stops for SNR = 2 (13 stops for SNR = 1).
Noise kicks in, hence about one stop is lost vs ISO 800. This is still a very good result.

Fig.3: Step chart waveform plot of the UMP 4.6k at ISO 3200: noise kicks in, and about one stop is lost vs. ISO 800, leading to around 12 stops of dynamic range.

4.6k RAW DNG (lossless) dynamic range results

Similar to BRAW, we have to develop the RAW DNG files in DaVinci Resolve in order to export keyframes for analysis in the IMATEST software.
Interestingly, the dynamic range results of the Cinema DNG files without postprocessing are lower than with ProRes and also BRAW, coming in slightly above 11 stops untouched (SNR = 2). The DNG files exhibit much more noise than BRAW and ProRes, hence leading to a lower dynamic range reading in IMATEST. This is a similar phenomenon as we observed with the BMPCC 4k. Using postprocessing like the highlight recovery feature in Resolve along with noise reduction lifts it above ProRes and BRAW (I played around and was able to get more than 13 stops at an SNR = 2, and almost 14 stops for SNR = 1).

Fig. 4: dynamic range comparison of the UMP 4.6k (BRAW) ISO 800 result with other cameras. It fares very well, coming in one stop higher than the BMPCC4k.

Conclusion

When testing the various codecs on the UMP 4.6k there are clear signs of internal noise reduction going on in ProRes and BRAW, very similar to what we observed with the BMPCC4k (please watch particularly the end of our BMPCC4K review for an insight into our testing procedure for dynamic range).
Speaking of the BMPCC4k, the UMP4.6k overall comes in one stop higher with regards to the dynamic range. Impressive. However, I cannot reproduce the 15 stops dynamic range that Blackmagic Design are claiming, even at a signal to noise ratio SNR = 1 the maximum I was able to squeeze out by heavy post-processing was about 14 stops. In contrast to this, I was able to confirm the 13 stops for the BMPCC4k at SNR = 1, thereby confirming Blackmagic’s statements.
Therefore the untouched BRAW ISO 800 SNR = 2 (or 1/SNR = 0.5) dynamic range result will be the cinema5D reference for future dynamic range comparisons with other cameras.

We know that many of you are waiting for an overview chart of all our dynamic range and other technical tests, and please stay tuned for a bit, we are still working on it. There’s a lot of parameters to think about, and also it’s not so easy to display elegantly on our site – however it won’t be long until we will share it with you!

You can find Nino’s Ursa Mini Pro Hands-On video review by clicking here and Johnnie’s review and “real world footage” by clicking here.

Did you already work with the URSA Mini Pro 4.6 in RAW recording mode? If yes, What is your impression? Please share your experience with us in the comments below.

Fascinated by the new possibilities with new small cameras. Passionate shooter who isn't doing this for a living. Cut my teeth on the Panasonic GH series, always looking to keep the gear as small as possible on my travels through the world, where I try to tell cinematic stories as a hobby.

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Fascinated by the new possibilities with new small cameras. Passionate shooter who isn't doing this for a living. Cut my teeth on the Panasonic GH series, always looking to keep the gear as small as possible on my travels through the world, where I try to tell cinematic stories as a hobby.

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Did you run a black balance calibration after updating the firmware to v6.0 and before running the test? I’ve found that running the black balance can really improve the noise performance on Ursa Mini Pro, and it’s absolutely necessary to run it after every firmware update.

Thanks for the hint Jamie, no we didn’t do a blackbalance – but good to know and thanks for sharing that experience.

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December 12, 2018 22:33

Member

Jamie LeJeune

In my experience when the black balance is out it can make a 1 stop difference in noise, and running your test without running a proper black balance first quite likely explains why your results for the 4.6K are much lower than BMD’s own claimed stats. It also makes your current test results unreliable. I fully appreciate that it must be tough to work with unfamiliar cameras, but for every camera model out there, you have readers/followers who are owner operators of those cameras. For future tests, it would be a good idea to reach out and get some detailed knowledge from skilled owner operators of each camera model before you run tests.

Hi Jamie, I find it a bit hard to believe that black balancing should make such a huge difference in DR – when we first looked at the camera two years ago it wasn’t even available, it came later with a firmware update (4.2 or so I believe). Also, I thought that blackbalancing typically removes color cast in shadows (like a blue cast for example) but will not change the noise structure / pattern of the camera. If thats different with the way BMD implemented it, fine and good to know. In any case, it is what it is, and I appreciate your feedback about your experience with the camera. So, in the end the results we present are the DR results if you don’t do a black balance.

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December 13, 2018 16:19

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Jamie LeJeune

I can only report what I’ve seen in my own extensive use of the camera ¯\_(ツ)_/¯ It does make sense, however, that when the black balance is out, noise will go up because noise on every digital sensor is most prominent in the blue channel, so if that blue channel is raised in the shadows by an uncalibrated black balance, the bottom of the signal will be disproportionately noisy. And, that is exactly my experience whenever I’ve updated the firmware on the BMD Ursa Mini Pro and viewed (or accidentally shot) images before recalibrating. If you find it hard to believe, you’ve got the gear, so I respectfully suggest running a comparative test to see for yourself.

Hi Jamie, we will do a retest today. Any other suggestions that you have, or experiences you want to share?

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December 14, 2018 09:08

Member

Jamie LeJeune

Glad to know you are retesting. You should see some higher numbers in the results after calibration.

The procedure for black shading is covered on p115 of the current Ursa Mini manual.

How are you processing the BRAW signal in Resolve? There are 3 options in the raw tab — film, video, and extended video. And beyond that there are sliders to affect the contrast curve and the highlight and shadow rolloff. These settings all affect the distribution of the available stops, and I would assume affect your test as well. Or are you doing your own expansion from log using the curves control or LGG?

The Kelvin setting of the camera also affects noise performance in the shadows — tungsten balance at 3200K has more noise than daylight balance at 5600K. This isn’t unique to the Ursa Mini Pro (Art Adams describes the effect here: http://www.dvinfo.net/article/optical-science/sensorcolorbalance.html), but it is more noticeable on cameras that don’t have any noise reduction in the internal processing like the URSA Mini Pro, compared to cameras like the C300 and FS7 that do add noise reduction to the processing.

In your article you stated that BMD is applying noise reduction to the internal processing, but my understanding is that this is not the case. The new firmware does have a new debayer designed to reduce false color/detail relative to the previous debayer, and the result is likely cleaner than the old debayer, but it’s not noise reduction per se. I’d suggest reaching out to Captain Hook at BMD for confirmation on that point.

Doing a black balance is standard procedure on most cameras. certainly after a firmware update. others like canon will even say after ISO change and certainly if the camera has taken a major in change in tempeture – the hot and cold kind. So honestly that kind of killed the accuracy of the tests.